This invention relates to a sun heating equipment which comprises at least one sun collector, which sun collector comprises at least one upwards-facing hollow tightly closed absorbing plate which is provided with an inlet and an outlet and which has at least one flow channel which connects said inlet to said outlet, which equipment further comprises a line for heat-transfer fluid which connects the absorbing plate outlet to the inlet thereof, means to remove heat from the fluid inside said line and means for generating a vacuum inside said absorbing plate.
Such a sun heating equipment is known from U.S. Pat. No. 4,134,390.
The sun heating equipment according to said U.S. Patent comprises a number of hollow absorbing plates which are formed by two metal panels secured against one another which are provided with such depressions as to form between said panels flow channels for the heat-transfer fluid, which channels connect the inlet at the bottom of said absorbing plate to the outlet at the top thereof. A circulating pump in that line which connects the outlets of said absorbing plates to the inlets thereof, pumps said fluid in liquid form to the absorbing plates where said fluid vaporizes. Said fluid then leaves in vapour form the absorbing plates and condenses inside a condenser heat exchanger which is mounted upstream of said circulating pump in the line.
A storage tank is mounted in parallel relationship with said condenser/heat exchanger. The vaporizing of the fluid inside said absorbing plates is enhanced due to a vacuum prevailing inside the absorbing plates. Said vacuum is generated by a vacuum pump which is mounted at the end of a branch line, which branch line connects between two valves to the parallel line wherein said storage tank is mounted. During the normal operation of the equipment, said vacuum pump does not work, but the pressure inside the absorbing plates is low enough to cause all of that liquid fed inside the absorbing plates to be vaporized at a a selected temperature. The equipment comprises a control device which controls notably said valves and vacuum pump. Said control device insures that said vacuum pump starts operating and can restore the vacuum inside the absorbing plates when the pressure inside said absorbing plates has become too high. The control device also controls the operation start of the vacuum pump when the temperature of the absorbing plates lies below said selected temperature. The valves are thereby so operated as to have said vacuum pump suck out the absorbing plates and the liquid from said plates collect in the storage tank. There is thereby no danger that the fluid in liquid form which completely fills the bottom of the absorbing plates, freezes as at low temperature, the absorbing plates are emptied. Such equipment does however include a quite intricate control device and the working thereof is quite irregular as the feeding of heat-transfer fluid to the collectors is stopped whenever the temperature of the absorbing plates is too low or the pressure inside said plates is too high. The start of the vacuum pump working when the equipment operates results in the moisture inside said pump condensing and being removed from the circuit. After some time, the equipment will become completely dry and will stop working. Moreover, the vaporizing of the water inside the absorbing plate will occur through the boil phenomenon as the absorbing plate is necessarily filled with water, whereby an irregular working with water conveying occurs and no normal working of the condenser is possible. Due to the relatively large liquid mass inside the absorbing plate, the heat inertia of the equipment is quite strong.
The invention has for object to obviate said drawbacks and to provide a sun heating equipment which has a quite simple structure and does not require any intricate control device, whereby the collectors have a small heat inertia, do not have to be emptied to avoid damages due to freezing, and allow a very good heat transfer between said collectors and the heat-transfer fluid.